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MCQ
81. A circuit breaker is essentially-
an automatic switch
a manual switch
a high-lightning arrester
none of the above
ব্যাখ্যা: A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by excess current from an overload or short circuit.
82. The most severe fault on the power system is-
there phase short circuit
line to line fault
double line to ground fault
single line to ground fault
83. The operating speed of a relay depends upon the-
Rate of flux built up
Armature core air gap
Spring tension
All of these
84. An isolator is designed to open a circuit--
full load
normal condition
no load
all of the above
ব্যাখ্যা : An isolator is designed to open a circuit under no load Its main purpose is to isolate one portion of the circsil from the other and is not intended to be opened while current is flowing in the line
85. Most faults occurring in the field are in-
CTs and PTS
switchgears
overhead lines
cables
ব্যাখ্যা: Most faults occuring overhead lines. Because in raining day, there is more probability to occur fault. Leakage current and short circuit current frequently occured an raining day
86. A permeable substance is one--
Which is a good conductor
Which is a band conductor
Which is a strong magnet
Through which the magnetic lines of force can pass very easily
87. Fault level means-
fault current
fault MVA
voltage at the point of fault
none
88. 8A generator supplies 100 MVA at 0.5 power factor. What is in MW?
100
90
200
None
89. Under normal operating conditions, the contacts of the circuit breaker remain-
closed
semiclosed
open
none of the above
ব্যাখ্যা: Under normal operating conditions, the contacts the circuit breaker remain closed. When any fault occart the contact is opened.
90. In SF6 circuit breakers, the SF, gas-
has insulating properties
is non-inflammable
is non-poisonous
all of the above
91. The relay operation coil is supplied through-
fuse
power transformer
current transformer
none
ব্যাখ্যা: The relay operating coil is supplied through current treansformer. Current transformer is used to measure the current as the indication for relay.
92. Inverse time current relays are used for the protection of-
Feeders
Transformers
Alternators
Both A and B
ব্যাখ্যা: Inverse time current relays, operating time is inversely changed with current So, hich current will operate over current relay faster than lower ones. It is used feeders and transformers
93. IDMT relays are used to protect the power transformers against-
External short-circuit
Overloads
Internal short-circuits
Both (a) and (b)
94. Breaking current is a value.
RMS
Maximum
Average
Any of the above
95. SF6 gas is used as it has-
High-boiling point
Electronegativity
Good conductivity
None
96. Which of the following circuit breaker is highly reliable and has a least maintenance?
Oil circuit breakers
Air blast
Vacuum circuit breakers
SF6 circuit breakers
97. A fuse is a--
protective device
current limiting device
current controling device
none of the above
ব্যাখ্যাঃ in electronic and electrical engineering, a fuse is an electrical safety or protective device, that operates provide overcurrent protection of an electrical circuit
98. Primary winding of CT is connected--
In series with the load
In parallel with the load
Between line and neutral
Both (a) and (b)
ব্যাখ্যা: The primary winding of the current transformer(CT) is connected in series with the transmission line whose current is to be measured where the potential transformer (PT) is connected in parallel with the line
99. বাংলাদেশে কয়টি ন্যাশনাল গ্রিড লাইন আছে?
1 টি
3টি
2টি
4টি
100. Differential relay is used for protection of--
Transmission line
Equipment having windings
Distribution line
None